Shallow, colluvial landslides are a common occurrence in many areas. This type of slope failure requires preventative action for both stability and aesthetic reasons, especially around existing homes. Many of existing methods of landslide mitigation and slope stabilization are aimed at stabilizing large slopes with large project volumes and costs. An effective, relatively small-scale method for stabilizing shallower, colluvial hillsides that are at or near failure is needed.
Research on mitigation techniques for shallow, colluvial landslides has seen some interest from the geotechnical community in the past 20 years, although most research has been performed on the predictive analysis of these types of slides (e.g. Aubeny and Lytton, 2004; Cho and Lee, 2002; Collins and Znidarcic, 2004; Iverson, 2000). While predictive analysis techniques are an important aspect of understanding slope stability behavior, they do not always assist communities faced with impending landslides. Instead, a method of preventing or arresting the movement of the slope mass is needed.
Existing methods of landslide mitigation have been summarized by Rogers (1992). They include excavation and recompaction, conventional retention structures, subdrainage, soil reinforcement using geomembranes and geosynthetics, mechanically stabilized embankments, and combination mechanically stabilized retention structures.
Unfortunately, most of these mitigation options are not applicable to shallow translational slides, mainly due to economic considerations. Retention structures, soil reinforcement options, mechanically stabilized embankments, and combination structures all require large volumes of earthworks in addition to comparatively expensive and time consuming installation methods. These techniques require excessive effort and time that is not warranted when mitigating shallow landslides that are small in area, on the order of only several tens of square yards. For these types of slides, only excavation and subdrainage techniques are applicable. However, these techniques require a substantial on-site and slope renovating presence. The present invention minimizes the need for large machinery and thereby allows slopes stabilization behind existing homes, and in other areas with limited access. Further, the method may be rapidly deployed so that slides may be prevented prior to full mobilization of the slide mass.
Others, such as Ito et al. (1981, 1982), have addressed rotational landslides. These deep landslides have been mitigated with extremely long (25 to 100 feet) columns (piles) placed in a portion of the potential slide area, generally at the toe of the slope to lock down the base of the potential slide. However, these long, heavy piles are inappropriate for shallow, translational slides. The present invention allows for locking down the entire potential slide area by placing relatively small, lightweight plate piles throughout the entire potential slide area.
Patents have issued describing some of the above-mentioned techniques. Devices and techniques for large scale slope stabilization are described in U.S. Pat. No. 2,880,588 issued to Moore, U.S. Pat. No. 5,797,706 issued to Segrestin et al., German patent number DE 4226067 issued to Hermann, and Japanese patent number JP 57071931 issued to Yoshihisa. These large-scale retaining walls require the use of heavy equipment, and are unsuitable for stabilizing smaller, less accessible slopes.
Other patents deal with stabilizing soil that is adjacent to water; for example U.S. Pat. No. 1,073,278 issued to Mosher, U.S. Pat. No. 3,412,561 issued to Reid, and U.S. Pat. No. 6,659,686 issued to Veazey. However, these patents do not specifically address slope stabilization of colluvial, sloping soil masses.
Still other patents describe the use of posts or anchors. See e.g., U.S. Pat. No. 1,408,332 issued to Zimmerman, U.S. Pat. No. 1,433,621 issued to Hutton, U.S. Pat. No. 4,530,190 issued to Goodman, U.S. Pat. No. 1,109,020 issued to Skiff et al., U.S. Pat. No. 6,666,625 issued to Thornton, and D334,121 issued to Van Handel III. These patents all assume that the piles will be used in conjunction with fencing. None of these patents teach the technique of placing stabilizing plate piles in a manner to prevent or reduce shallow colluvial landslides.